Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen orportion thereof with a graphical user interface showing our new design;

FIG. 2 is a front view of a second embodiment thereof; and,

FIG. 3 is a front view of a third embodiment thereof.

The outer broken lines showing a display screen or portion thereof formno part of the claimed design. The remaining broken lines showingportions of the graphical user interface form no part of the claimeddesign.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.